Hi Socketman,
I'm glad you're enjoying your new Axioms, and sorry you're experiencing a rattle in one of the M2s. Try removing the grille cover and slightly tightening the screws that hold the woofer and tweeter to the front baffle. Don't over-tighten them, but they should be snug. That might eliminate the rattle.
If that doesn't help, you can remove the woofer and check the wires that lead from the woofer (and tweeter) to the crossover. It might be just be a wire rattling against the aluminum frame (basket) of the woofer. You won't void your warranty by checking. If that's what it is, just dress the wire to one side away from the aluminum basket.
Regards,
Alan
